The present invention relates to a method of manufacturing a tubular member made of synthetic material and to a tube and a sheath manufactured by the method.
The invention applies in particular to making optical fiber cable networks.
Usually, an optical fiber cable comprises a plurality of optical fibers housed in a sheath made of synthetic material, in particular extruded synthetic material. In most optical fiber networks, cables are housed in tubes that are generally made of extruded synthetic material. In order to thread an optical fiber cable into a tube, various methods are used, in particular blowing and carrying methods. In a carrying method, the optical fiber cable is pushed into the tube by being entrained in a flow of air under pressure that is injected into the tube. The effectiveness of the carrying method is limited, in particular by friction between the outside surface of the sheath of the optical fiber cable and the inside surface of the tube.
In addition, the effectiveness of a blowing method is limited, in particular by friction problems.
A particular object of the invention is to optimize the effectiveness of mounting an optical fiber cable in a tube by a conventional carrying or blowing method.
To this end, the invention provides a method of manufacturing a tubular member made of synthetic material, the method being of the type in which the tubular member is extruded, and during extrusion of the tubular member, the extruded synthetic material is subjected to a flow of water in liquid or steam form that comes into contact with the inside or the outside surface of the tubular member in such a manner as to form crevices in the surface of the tubular member that comes into in contact with the flow of water, the surface including the crevices being known as the xe2x80x9clow-friction surfacexe2x80x9d.
According to the characteristics of various implementations of the method:
the extruded synthetic material is subjected to a flow of water in liquid form;
the flow of water comes into contact with the inside surface of the tubular member;
the tubular member is extruded in an extruder head including a duct for injecting the flow of water into the vicinity of the inside surface of the tubular member;
the duct for injecting the flow of water into the vicinity of the inside surface of the tubular member is a duct for injecting a lubricant into contact with the inside surface of the tubular member, the water being injected into the lubricating duct instead of the lubricant;
the flow of water comes into contact with the outside surface of the tubular member;
the flow of water is injected into a nozzle directed towards the outside surface of the tubular element;
the synthetic material is a thermoplastics material; and
the synthetic material is polyethylene.
The invention also provides a tube to form a housing for an elongate member such as a cable, in particular an optical fiber cable, the tube being manufactured by a method as defined above, the inside surface of the tube being the low-friction surface.
The invention further provides a sheath for a cable, in particular an optical fiber cable, the sheath being manufactured by a method as defined above, the outside surface of the sheath being the low-friction surface.